OTEC (Ocean Thermal Energy Conversion) plants use the temperature differential between the warm surface water (80° F., 26.7° C.) near the equator and the cold deep water (45° F., 7.2° C. at 1,500 feet) to produce electrical power. For OTEC, the temperature differential is 19.5° C. An OTEC power plant has been operating in Hawaii for many years. Since the temperature differential is so small, the efficiency is low (about 3%), but since there are huge quantities of warm and cold seawater available, it is a good source of energy. These plants use a refrigerant, such as propylene or ammonia as a working fluid.
Many geothermal power plants also use refrigerants as the working fluid, since the temperatures are too low to use water effectively.
In prior art, my patent U.S. Pat. No. 6,006,538, entitled “Air Conditioner Energy System,” describes an engine that produces cool air and produces power. It is not as efficient as the invention described herein, because it does not use the cooled air for pre-cooling the air that flows to the condenser.